Wednesday, April 11, 2012

NEWS: The Neuroscience behind the story

I've got to say that I think I have some of the greatest friends and fans in the world. Just today I was wondering what topics to use for blog posts over the next week or so. Unfortunately, it seems that I am going to be dealing with carpal tunnel syndrome for some time, so I need to get used to dictating the blogs, and I was worried about what content would be appropriate for dictation.

So today in Facebook, I received a message asking my opinion of a recent article on cracked.com. Now, normally cracked.com is funny, satirical, or just plain strange. However, they really do have some interesting articles in this is one that I thought was worthy of comment on this blog. The article with the following link (http://www.cracked.com/article_19518_5-seemingly-random-factors-that-control-your-memory.html) described find seemingly random factors that control our memory. I think I'll take these one or two at a time and tell you a little bit about the neuroscience that actually explains the strange phenomena.

The article starts out by saying "We have all experienced zone out moments when we totally should remember something that has apparently been deleted from our brains hard drive against our will. That's because the human brain is a haphazard messy machine that glitches at the slightest strangest provocation. However our old friend science has tracked down some the completely random things to decide whether or not your memory will choose to function at that particular moment. Things like: #5 Walking through doorways." the section goes on to describe the following scenario: you walk into a room, you know you came in here to do something, but you can't remember what it was. You try to remember and end up retracing your steps: did you come from the kitchen? Did you come from the bedroom? Was there something in this room that you wanted or needed? Once you begin to retrace your steps, you remember what it was that you were trying to do in the first place. According to the article, the trigger for your memory was walking through the doorway; your memory partitions information into folders, much like your computer hard drive. Those folders are organized by events which includes changing spatial locations such as walking through the doorway.

so now we know what cracked.com has to say about "doorway" memory, which is neuroscience really have to say about this? Well, it's true. The brain actually does organize information, according to what we would normally call "contexts". I've mentioned on many previous blogs that memory involves association, and those associations can be many types of information. A very important type of context is spatial context. One of my favorite brain areas, the hippocampus, is involved in the representation of place and spatial relationships. Back in the 1970s, to scientists discovered that cells in the hippocampus of rats were active only when that animal was in a particular place and its environment (O'Keefe J, Dostrovsky J (November 1971). "The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat". Brain Res.34 (1): 171–5). Following these findings neuroscientists who study the hippocampus have spent 40 years defining the spatial mapping properties of neurons in this part of the brain. We learned many things, that memory for places is a very important context for memory in general. We've learned that the act of walking from one space to another, through a doorway or small opening, causes the spatial memory to reset and the new map to be formed. We learn that taking an animal out of a known, well explored area, and putting the animal back in later causes the same map. To "appear" in the activity of hippocampal neurons. We've also come to know that information that needs to be remembered, occurring at different spatial locations, is encoded differently.

Thus it is quite true that walking through doorways can re-trigger memories and help us to remember what it is we entered the room to do. However, it's a little bit more complex than that, for it is not just walking through the doorway, but retracing our steps that is important. As neuroscientists study place cells and spatial representation, we discover that there are number brain areas involved in mapping the pathway or trajectory that a subject takes through their environment. There are cells in in Toronto cortex that appear to create a "grid" upon which a cognitive map is formed. There are neurons in brain areas surrounding hippocampus that encode the direction that a subject is pointing or looking. There are also neurons which appear to encode only particular trajectories: they may fire when the animal goes through a particular location, from right to left, but not when the animal goes through the same location from left to right. Together, all of these neurons form a system known to neuroscientists as "path integration." Just as much as spatial location is an important context for memory, the pathway or trajectory that subject follows is also important context for memory. Therefore, it's not just walking through the doorway, but retracing one's steps, in order to jog your memory and recall what you forgotten. In many ways it's just like trying to remember the title of the song. You can remember some of the lyrics, but not the title. So if you start this to sing the song to yourself, all the way to the end of the verse and back to the beginning, you can quite frequently remember the title because now you have the full context.

And as I've stated in other blogs, when it comes to memory, context is everything.

In the next few blogs I continue with this article and talk about two additional factors that help jog your memory, and even assist in forming the memory in the first place. Until next time, keep walking through those doorways!